In a typical oil or gas well, a blowout preventer (“BOP”) controls the flow of fluids both into and out of the well during the drilling process. Although blowout preventers come in a variety of styles, sizes and pressure ratings, they generally have several different valve systems. Some valve(s) may be able to completely close the wellbore, others may seal around the tubular components of the well, and yet others are fitted with shearing surfaces that can cut through drill pipe to effect a complete seal. A situation may occur during drilling in which the crew loses pressure control of the well. This situation is known in the art as a “kick”. When a kick happens, and the BOP fails, fluids such as gas, oil, and/or water rush up to the surface. This sudden rush may cause a blowout, which could lead to catastrophic damage, explosion, fire, and loss of life. When a BOP fails, and it is determined that the BOP cannot be closed properly by some alternate means (e.g., by using remotely operated vehicles), then oil/gas/water would continue to flow from pipes that are connected to the BOP.
Both land-based and underwater-based wells employ BOPs. The failure of the BOP can occur on land or in an underwater environment such as in a lake or in the sea or ocean. A BOP can fail, for example, during a deep sea drilling operation. BOPs for deep sea drilling operations are connected to various pipes in an assembly that is known in the art as a “riser” assembly. One such pipe is known in the art as the “choke line”. Another such pipe is known in the art as the “kill line”. These pipes may be located at the bottom end of the BOP stack, or in some designs, may be located near the top of the BOP stack. These pipes are also connected to a drilling rig. The drilling rig for a deep sea operation may be a platform, a semi-submersible ship, or a drill ship located above the well on the water surface. Therefore, the riser, choke line and kill lines may be from a few feet to several thousand feet long, depending upon the distance from the drilling rig to the BOP stack held on the ocean floor.
After a BOP fails, there are ways to stop the uncontrolled flow of fluid such as oil and gas from the well. One of these ways is known in the art as a “top kill”. A “top kill” is sometimes used in combination with a “junk shot”. Another way to reduce or stop the uncontrolled flow of oil from a well after a BOP fails is called a “static kill”.
Another way for reducing or stopping the uncontrolled flow of liquids from an oil well after failure of a BOP is to drill a second hole that intercepts the uncontrolled oil well above a zone where the oil/gas/water is located, and afterward, to close the well by cementation. This method of stopping uncontrolled release of fluid from the well is sometimes referred to in the art as a “bottom kill”.
Each of the above methods for reducing or stopping the flow of oil from a well after a BOP fails has its limitations. Any of them might fail in a deep sea environment. In the recent 2010 disaster in the Gulf of Mexico, for example, a deep sea oil well experienced a kick and the BOP for the well failed. The result was that oil/gas/water flowed uncontrollably from the well into the Gulf of Mexico. The drilling rig for the well was a semi-submersible drill ship. The initial kick to the drilling rig resulted in an explosion, fires on the drilling rig, and loss of life. Later, the drilling rig sank into the Gulf of Mexico and the riser assembly snapped, which resulted in an uncontrolled release of oil/gas/water from the undersea well into the Gulf of Mexico. This uncontrolled flow from the undersea well continued for several weeks.
Various methods were attempted to stop or stem the flow.
A “top kill” method was attempted to provide enough back pressure to stem the flow of oil. Heavy drilling mud was pumped into the blowout preventer “choke line” and “kill line” and down into the oil well.
A “junk shot” was attempted in combination with the “top kill” wherein junk material (pieces of rubber, golf balls, short lengths of rope, etc.) were included with the drilling mud to try to plug the orifices within the BOP.
Neither of the above attempts were effective.
The uncontrolled flow was finally stopped after the operators performed a “bottom kill” method that involved drilling a secondary hole into the original well and subsequently creating a cement plug in the original well.
Better methods for reducing or stopping the uncontrolled flow of fluids such as oil and gas from wells are needed to minimize the damage caused by these potential disasters.
Therefore, an object of the present invention is a method for reducing or stopping the flow of fluids such as oil and gas from an oil well after a blowout preventer fails.